PURPOSE: To permit a master station only to once transmit a synchronizing signal and a command so as to collect data of all slave stations by permitting the master station to put all ID of the slave stations whose data are to be collected in the command transmitted by polling in the order of data collection.
CONSTITUTION: A data communication system consists of the master station M and the plural slave stations S1-S3, which are connected to a common communication line in a multi-drop form, and the master station M collects data of all the slave stations S1-S3 by polling. A period from time when the master station M once transmits at least a data communication request CMD to all the slave stations S1-S3 to time when the respective slave stations S1-S3 sequentially finish transmitting at least self station data D1-D3 consisting of the generated data of the self stations and station numbers is set to be the one cycle of data collection. Since data for n-stations can be collected by one synchronizing signal SYN and one command CMD, communication time required for collecting data for n-stations can be shortened.
MAKITA YUKIO
SUGINO KAZUHIKO
FUJI FACOM CORP